The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also be inventions.
Numerous systems have been designed to allow for repeated construction and deconstruction of structures. Such arrangements generally allow a variety of different parts to work together as a unified system with common attachment geometries or methods allowing individual parts to be reconfigured to create new forms. One common part interlock method used is that of an interference fit, also known as a press-fit. Despite the building flexibilities provided by press-fit attachment methods, there are also some common drawbacks, such as difficulty of assembly, and later disassembly, especially by younger children, and generally the inability to remove an internal part without first removing parts attached thereupon.
Magnetic construction inter-connects can facilitate the process of connecting parts into structures, through natural magnet attraction, as well as the process of detaching parts, even allowing internal, bounded parts to be slid out and replaced. Magnetic construction systems vary significantly in terms of how this magnetic coupling is achieved. Some systems may employ permanent dipole magnets fixed within a structural body with magnet polarity oriented perpendicular to the body surface. As a result, attaching two or more parts requires proper orientation of structural bodies such that magnetic polarities are aligned. However, this fixed dipole arrangement means a user has a 50% chance of needing to flip any given piece prior to attachment. For multilayer systems, it may difficult, if possible, to flip a connecting part, especially parts having multiple magnets which all must have a proper predetermined orientation. For parts that are not manufactured in a specific way with specific magnetic orientations, some construction options are excluded.
Other magnetic construction systems may address this polarity alignment issue by adding an intermediate ferromagnetic piece which can attach equally well to either the north or the south pole of any dipole magnet. However, the need for a separate ferromagnetic part impacts system architecture, ease of construction, safety, and overall cost.
Similarly, some magnetic construction systems may employ loose magnets to attach structural bodies at ferrous attachment points. However, this approach has corresponding shortcomings, and brings up the additional safety concerns associated with the risk of children ingesting two or more loose magnets and having them internally magnetically couple.
A fourth approach could involve a use of captive magnets which are free to rotate within structural bodies, allowing self-alignment of their magnetic polarities when the magnetic fields of adjacent magnets sufficiently overlap, such as when parts are adjacently positioned for magnetic coupling. Some systems could employ cylindrical permanent dipole magnets positioned proximate to linear perimeter edge surfaces of geometric forms, such that the geometric axis of each cylindrical magnet is parallel with an adjacent linear perimeter edge surface, and the polar axis is perpendicular to the geometric axis. Clearance between each magnet and corresponding magnet retaining pocket within the structural body may allow each magnet to swivel freely about its cylindrical axis, allowing the polar axis of any magnet to align with the polar axis of any magnet in an adjacent part. Accordingly, adjacent parts may be able to magnetically couple along their linear perimeter surface segments and to pivot with respect to the linear contact between said perimeter surface segments. This architecture may remove any need to actively orient parts to align magnetic polarity for part coupling. However, one notable result of this architecture in which the rotation axis of the cylindrical magnet is perpendicular to the polar magnetic axis is that two magnetically attached parts find magnetically stable attraction at increments of each 180 degrees; when one part is twisted about the magnetic axis of attachment, the magnets provide rotational resistance (by virtue of the magnetic fields attracting the magnets to a position of parallel cylinders) until the associated magnet has been rotated past 90 degrees, at which point the respective magnetic fields then attract the magnets to the next stable orientation of parallel axes of the cylinders, 180 degrees from the last stable position. This bi-stable coupling behavior may be considered desirable in one respect, by helping part edges to align along their linear edge geometry, but it also means that this magnet architecture it not suitable for applications in which smooth and continuous rotation is desirable, such as with magnetically attached wheels, gears, or chain segments. Furthermore, the combined thickness of two intermediate part walls between coupled magnets reduces magnetic coupling force significantly, therefore requiring larger or stronger magnets for any desired connection strength and commensurately increasing overall system cost.
Some systems may make use of an internally captured spherical dipole magnet which is free to swivel within a retaining pocket to match the polarity of a like magnet in an adjacent piece. Two such magnetically coupled parts could rotate with respect to one another but may experience considerable rotational friction between contact surfaces due to the local clamping load applied by the respective magnets. Again, this could be a shortcoming for applications where low-friction, smooth/continuous rotational movement is desired, such as with wheel or gear axles, and wall thickness would meanwhile detract from magnetic coupling force. Furthermore, such a magnetic coupling may not provide sufficient rotational stability to allow for stable structures, especially when the magnetic coupling axis is oriented horizontally and the weight of attached parts may cause unwanted rotation or bending/sagging of parts about said axis.
Other systems may employ an alternate mechanisms to achieve a similar effect. In one architecture, cylindrical magnets may be orientated with the geometric axis of each magnet perpendicular to the adjacent body surface, and the polar axis of the magnet perpendicular to the geometric axis. Each magnet could freely swivel only about its cylindrical axis, such that the polar axis remains parallel with the respective body surface. If two or more such parts are positioned for magnetic coupling, the respective magnets may self-orient with parallel and opposed polarities. Parts may rotate with respect to one another about this magnetic coupling, via the capability of either magnet to rotate within its retaining pocket, but the interposing surfaces may experience significant friction due to the clamping force exerted by the magnets, thereby resisting rotation, while the wall thickness of the retaining walls detracts from the coupling force of the magnets.
Still other systems may include a rather complex pivotable subassembly comprised of a disc shaped magnet with a polarity coaxial with its geometric axis, and a pivotable carrier which allows the magnet to axially rotate perpendicular to the polar axis so that either magnetic pole may face outward. Two of the magnetic subassemblies may thereby respectively swivel to magnetically align, enabling attachment of corresponding structural bodies. This magnetic coupling may allow relative rotation of either structural body about the shared magnetic axis when an applied rotational force overcomes related friction between contact surfaces. However, this system has no provision for providing rotational stability between coupled structural bodies when so desired, and requires multiple additional parts for the subassembly required in each magnet location.
A further variation may provide that each of the relatively complex pivotable magnet holder subassemblies has built-in circumferential teeth which index with like teeth in other pivotable subassemblies. In this arrangement, relative rotation of magnetically coupled parts is always achieved in an indexed fashion, and is not capable of free rotation when so desired. As before, the part count and complexity of each pivotable magnetic subassembly translates to increased overall cost.
In summary, various magnetic construction systems may employ different mechanisms and methods of aligning magnetic polarity between parts, but not in a manner which comprehensively enables self-alignment of magnets via geometric rotation while also enabling any magnetic coupling to serve either as a freely rotatable, low-friction axis of rotation when desired (such as for wheels, gears, or chains links), or as a rotationally stable connection point with indexed rotation detents suitable for structural stability. Therefore, to provide the greatest utility in further expanding construction capabilities, what is needed is a magnetic construction system with self-aligning, exposed magnets and a capability to allow either free or indexed rotation between magnetically coupled parts.